Device for electron-beam heating of materials mainly for their melting and evaporation

ABSTRACT

A device is disclosed which relates to devices for vacuumheating of materials. The device for electron-beam heating of materials, preferably for their melting and evaporation, comprises an electron-beam gun forming a ribbon electron beam; and an electromagnetic system for controlling said ribbon electron beam with a closed magnetic circuit having a rectangular shape and cores in which deflection coils are disposed, said device according to the invention being characterized in that the deflection coils are located on long opposing cores of said magnetic circuit, the short opposing cores of said magnetic circuit being mounted with additional coils for correcting and scanning of said beam, the deflection, correction and scanning coils being electrically associated with each other. The device may prove useful for melting and evaporation of metallic and nonmetallic materials.

MTROQ KR 3381.4!829 '1 United States Patent 1 an 3,814,8c9 Movchan et al. June 4, 1974 [54] DEVICE FOR ELECTRON-BEAM HEATING 3.622.679 ll/l97l -Kennedy um OF MATERIALS MAINLY FOR THEIR MELTING AND EVAPORATION Primary li.\'uminw'-Roy N. Envall Jr. "[76] Inventors: Boris Alexeevich Movch an, Ulitsa Almrmy' Axum or l4"vm H0lmun & Stem Darvina, 7, kv. 7; Viktor Alexandrovich Timashov, Ulitsa [57] ABSTRACT t .r 'i t r Lgkvymheslav A device is disclosed which relates to devices for f :11 I xa I vacuum-heating of materials. The device for electronk g f g g beam heating of'materials. preferably for their melting O f and evaporation comprises an electron-beam gun [22] Filed: July 28, 1972 forming a ribbon electron beam; and 'an electromag- 3 netic system for controlling said ribbon electron beam App! 276037 with a closed magnetic circuit having a rectangular shape and cores in which deflection coils are disposed, [30] Foreign Application Priority Data said device according to the invention being charac- OCL 36 197] 'U'SSR 170690] terized in that the deflection coils are located on long opposing cores of said magnetic circuit, the short op- [SZl U.S. Cl. 13/31 Posing Cores of Said magnetic Circuit being mluntcd [5|] I I g 05 7 with additional coils For correcting and scanning of [53] Field M Search 13 said beam, the dcllectiom correction and scanning coils being electrically associated with each other: The [55] References Cited device may prove useful for melting and evaporation UNITED STA-[F5 PATENTS of metallic and non-metallic materials.

330N222 h/Whtt Anderson .4 13/3! 4 Claims, 3 Drawing Figures MATERIALS MAINLY FOR THEIR MELTING EVAPORATION BACKGROUND OF THE INVENTION The present invention relates generally to devices for heating materials in a vacuum and more particularly, it

relates to a means for electron-beam heating of materials, preferably for melting and evaporation thereof.

Some time ago, electron-beam guns with linear cathodes formingelectron beams have found wide applications for vacuum-heating of materials. The direct heating of cathodes, the possibilities of enhancing the gun power by increasing the emitter area by increasing its length, and the use of accelerating voltages of up to 20 kV, with thesimplicity of construction, distinguish the afore-said guns with the ribbon beams from axial electron gims having similar designation. However, an increase in the width of a sheet beam as wellas constructional protection of a thermionic cathode from'vapors and sputtered molten material lead to considerable difficulties in beam control (deflection, focusing and scanning). This resulted in a more sophisticated construction of the devices.

Thus in the known devices (cf. US. Pat. No. 3,409,729 CI.l3-3l and No. 3,114,656, Cl.3l375), to protect the electron-beam guns forming ribbon electron beams from vapors and sputtered molten material and to produce a differential vacuum, use is made of several electromagnetic beam control systems disposed in succession along the beam path.-

Such devices, being relatively complicated in terms of their construction and featuring also large overall dimensions, require accurate matching of all the electromagnetic systems that are arranged in succession, but this fact materially impairs the reliability of operation of the above devices.

Also known are devices in which the deflection of the ribbon electron beam is effected by a single electromagnetic system comprising a rectangular closed magnetic circuit with short cores on which deflection coils are located generating a magnetic field which deflects the beam along the cathode, i.e., in the beam plane. However, constructional protection of the linear thermionic cathode from the vapors and sputtered molten material particles necessitates a substantial increase either in the length ofa beam guide having an outlet with the deflection system arranged thereat or in a beam deflection angle which augments the overall dimensions of the device (especially when its power is increased by extending the cathode length) which adversely affects the quality of the beam formation.

A serious disadvantage of the devices lies also in the fact that the beam can be controlled only in one plane, which diminishes substantially the technological potentialities of the devices.

SUMMARY OF THE INVENTION design being such as to ensure vacuum differentiation and protection of the electron-beam gun from vapors and sputtering. The device comprises a single-unit elec tromagnetic ribbonbeam control system which enables v a slightly divergent sheet beam formed by the electronbeam gun to be deflected at an angle of up to 45 and to be concurrently focused and converted into a cylin drical beam, ensuring also correction of the beam path and its scanning in a plane perpendicular to the dellection plane.

This is attained by a device for electron-beam heating of materials comprising an electron-beam gun forming a ribbon electron beam and an electromagnetic system of control of said beam with a closed rectangular magnetic circuit having cores with deflection coils are arranged thereto, according to the invention. the latter being disposed on the long opposing cores of the closed magnetic circuit, the short-opposing cores ofsaid magbeam.

Depending on the width of the ribbon beam, the opti- I mutn length ratio of the cores can be within the range The deflection coils as well as those for correction and scanning are advisable to be coupled with each other in series.

Fine focusing of the deflected beam during its conversion into a cylindrical one or its focusing into a nar row long focal spot is performed by changing the ampere-turn ratio in these coils by connecting by-pass adjustable resistors to them so as to produce a nonuniform magnetic field of a requisite shape.

To connect the above by-pass resistors, the neutral point of the series-connected COIIS is advisable to be provided with a lead-out.

For scanning and deflection of the beam over the metal heating surface, the correction and scanning coils can be coupled to a DC. current supply with an A.C. component having a pre-set amplitude and frequency. I

The device accomplished in conformity with the present invention has proved successful in solving a number of major technological problems encountered in the melting and evaporation of both metallic and non-metallic materials; a relatively small increase in only one dimension of the device (by increasing only the length of a linear emitter) enables the rated power ofthe device to be enhanced up to 400-500 kW with the accelerating voltages not exceeding 20 kV.

BRIEF DESCRIPTION OF THE DRAWINGS A fuller understanding of the nature of the present invention will be had from the following description of an exemplary embodiment of a device for electronbeam heating of materials mainly for their melting and evaporation and considered in conjunction with due reference to the accompanying drawings, wherein:

FIG. I is a sectional view of the device layout, according to the invention;

FIG. 2 depicts an electromagnetic system of the device, according to the invention, the shape of magnetic field and projections of three representative paths of the elements of a slightly divergent electron ribbon beam;

FIG. 3 is a wiring diagram of the coils of the electromagnetic system of said device.

DETAILED DESCRIPTION OF THE PREFERRED" EMBODIMENT As can be seen from FIG. I, the herein-described decathode focusing electrode '3 and an accelerating anode 4. With the aid of a beam guide 5 which is made in the form of a copper block fitted with passages 6 for cooling water and with rectangular openings for the passage of a ribbon beam 7, the accelerating anode 4 is designed to be coupled with an electromagnetic system of the device. which is a rectangular closed magnetic circuit 8.

Long cores of the magnetic circuit 8 carry two deflection coils 9 and 10 (FIGS. 1 and 2), its short cores being mounted two correction and scanning coils 11 and 12 (FIG. 2). The electromagnetic system is located in grooves of a copper water-cooled base 13 (FIG. 1).

As it is shown in the wiring diagram, each of the two deflection coils 9 and 10 (FIG. 3) and correction and scanning coils II and 12 disposed accordingly on the between the cores and are directed across the incoming 3 ribbon beam.

The length ratio between the short and long cores of the magnetic circuit 8 is chosen within the range of The slightly divergent ribbon beam 7 focused by the electron-beam gun and passing in the beam guide 5 is rectangular in cross-section (FIG. 2). The electrons passing in the transverse magnetic field of the deflection coils 9 and'l0, indicated in FIG. 2 by solid lines, are deflected at right angles to the intensity vector of the magnetic field.

Due to a certain curvature of magnetic force lines depending to a considerable degree on geometric dimensions of the rectangular magnetic circuit with the foregoing coils disposed on it, the sheet beam, on being deflected, is subject to the condenser effect directed to the middle deflection plane having a projection as shown by a straight line AB.

FIG. 2 depicts the projections of the representative paths of the ribbon electron beam onto a focal plane which in this case is a horizontal plane being level. with the point of collision between the beam and the object being heated.

At point "b" ofa section of the beam 7, the electrons passing through the concave magnetic ficld'are deflected at a certain angle to the middle plane AB. At points "a". m" and "n" the electrons are deflected in the middle plane AB. The electron path projections of these representative points are shown by the straight lines bb, mm", aa' and nn At point c" the electrons which have first reached into a convex field will move along the path cc and then, on being deflected into the concave field arc, are subjected within it to a prolonged effect and will follow the path shown ..by the linefc'cf directed also toward the plane AB.

Such interaction between the slightly divergent sheet electron beam with the magnetic field under consideration results in its deflection accompanied by a concurrent conversion of the sheet beam-into a cylindrical one and by its focusing into a focal spot 15 on the object being heated.

Decrease of the focal spot l5 along the axis CD and its increase along the axis AB is achieved by attenuation of the field of the deflection coil 10 which is ef-- fected by bypassing its turns with the aid of the adjustable resistor R (FIG. 2).

Decrease of the focal spot 15 along the axisAB and its increase along the axis CD is effected by attenuation of the field of the deflection coil 9 by bypassing it with the aid of the adjustable resistor R Correction (displacement) and scanning of the beam 7 along the axis CD are effected by the transverse field of the coils 11 and 12 shown in FIG. 2 by dotted lines.

Concurrent correction and scanning is achieved by 1 feeding the coils 11 and 12 with a direct current from a power supply E with an A.C. component of a pre-set amplitude and frequency.

What we claim is:

I. A device for electron-beam heating of materials, mainly for their melting and evaporation, said device comprising: 4

an electron-beam gun means forming a ribbon electron-beam and including an anode unit with an accelerating anode; an electromagnetic system including a closed magnetic circuit having a rectangular shape, said electromagnetic system beingdisposed in said anode 1 unit directly behind said accelerating anode for converting said ribbon electron-beam into a cylin- 'drical one; deflection coil means disposed on the long opposing cores of said rectangular magnetic circuit associated electrically with each other for deflecting said ribbon electronbeam in a plane perpendicular to-the plane of the beam, and correcting and scanning coil means disposed on the short opposing cores of said rectangular magnetic circuit and electrically associated with each other for deflecting said ribbon electron-beam over the surface of the material being heated. 2. A device as claimed in claim 1 wherein for focusing said beam in the form of a round spot on the surface of the material being heated, the length ratio between the cores of the magnetic circuit of said electromagnetic system is chosen within the range of l.25. I g 3. A device for electron-beam heating of materials, mainly for their melting and evaporation, said device comprising:

an eleetron-beanl gun means forming a ribbon clcctrotfbcam; an electromagnetic system including a closed magnetic circuit having a rectangular shape for controlling said ribbon electron-beam; deflection coil means disposed on the long opposing cores of said rectangular magnetic circuit associated electrically with each other for deflecting said ribbon electron-beam-in a plane perpendicular to the plane ofthe beam, said deflection coil means including coils which are series-connected for defleeting said beam being formed said seriesconnected deflection coils having a lead-out-from-- their neutral point to which b y-pass adjustable re sistors are coupled for providing a line focusing of said beam being formed; and

correcting and scanning coil means disposed on the short opposing cores of said rectangular magnetic circuit and electrically associated with each other and frequency. 

1. A device for electron-beam heating of materials, mainly for their melting and evaporation, said device comprising: an electron-beam gun means forming a ribbon electron-beam and including an anode unit with an accelerating anode; an electromagnetic system including a closed magnetic circuit having a rectangular shape, said electromagnetic system being disposed in said anode unit directly behind said accelerating anode for converting said ribbon electron-beam into a cylindrical one; deflection coil means disposed on the long opposing cores of said rectangular magnetic circuit associated electrically with each other for deflecting said ribbon electron-beam in a plane perpendicular to the plane of the beam; and correcting and scanning coil means disposed on the short opposing cores of said rectangular magnetic circuit and electrically associated with each other for deflecting said ribbon electron-beam over the surface of the material being heated.
 2. A device as claimed in claim 1 wherein for focusing said beam in the form of a round spot on the surface of the material being heated, the length ratio between the cores of the magnetic circuit of said electromagnetic system is chosen within the range of 1.2-5.
 3. A device for electron-beam heating of materials, mainly for their melting and evaporation, said device comprising: an electron-beam gun means forming a ribbon electron-beam; an electromagnetic system including a closed magnetic circuit having a rectangular shape for controlling said ribbon electron-beam; deflection coil means disposed on the long opposing cores of said rectangular magnetic circuit associated electrically with each other for deflecting said ribbon electron-beam in a plane perpendicular to the plane of the beam, said deflection coil means including coils which are series-connected for deflecting said beam being formed, said series-connected deflection coils having a lead-out from their neutral point to which by-pass adjustable resistors are coupled for providing a fine focusing of said beam being formed; and correcting and scanning coil means disposed on the short opposing cores of said rectangular magnetic circuit and electrically associated with each other for deflecting said ribbon electron-beam over the surface of the material being heated.
 4. A device as claimed in claim 3, wherein to provide the scanning and displacement of said formed ribbon beam over the metal surface being heated, said correction and scanning coils are connected to a D.C. current supply with an A.C. component of a pre-set amplitude and frequency. 